1902.] PUBLIC DOCUMENT — No. 33. 25 



Since 185)3 no phosphate has been applied to any part of 

 the field. The object in view in withholding phosphates 

 has been to test the lasting qualities of the several mate- 

 rials. At the beginning of the present season, supposing 

 the crops harvested to have been of average composition, 

 and that there has been no loss of phosphoric acid by leach- 

 ing (which is improbable), there must have remained of the 

 total phosphoric acid applied to the several plots the fol- 

 lowing- amounts in each : — 



Pounds. 



Phosphatic slag, 53.6 



Mona guano, .... 

 Florida phosphate, . 

 South Carolina rock phosphate, 

 Dissolved bone-black, 



29.7 



132.4 



102.0 



9.5 



Throughout the entire period of the experiment (1890 to 

 date), materials supplying nitrogen and potash have been 

 applied in equal amounts to all plots. Since 1893 the 

 quantities applied have been made very large, in order to 

 make it certain that the crops grown may find in the soil all 

 the nitrogen and potash they can possibly need. All the 

 plots in the field were limed at the rate of one ton to 

 the acre of quick-lime, slaked, spread after ploughing and 

 deeply worked in with a harrow in the spring of 1898. 

 The crops which have been raised on the field previous to 

 this } r ear, in the order of their succession, are potatoes, 

 wheat, serradella, corn, barley, rye, soy beans, Swedish 

 turnips, corn, oats and cabbages. Representing the yield 

 on the plot giving the highest returns by 100, the relative 

 efficiency* of the different phosphates at the beginning of 

 this year stood as follows : — 



Per Cent. 



Phosphatic slag, . . .100.0 



Ground South Carolina rock, 

 Dissolved bone-black, 

 Mona guano, 

 Florida phosphate, . 



92.3 

 90.7 

 88.3 

 71.5 



Taking into account the crops grown since 1895, when for 

 the first time a plot to which no phosphate was applied was 

 included, the phosphates have the following relative rank :* — 



* Swedish turnips, grown in 1897, have not been included in computing these 

 percentages as that crop was affected by disease not apparently connected with the 

 fertilizers used. 



